Indirect generation of steam by means of superheated heating steam



July 4, 1933. H. TRE'DE ET AL INDIRECT GENERATION 0F STEAM BY MEANS OFSUPERHEATED HEATING STEAM Filed Feb. 7, 1929 4 Sheets-Sheet 1 Fig. 1.

Fig. 2.

lavevnfirs: Han/6 Iiede and y 1933. H. TREDE El Al. 1,917,166

INDIRECT GENERATION 0F STEAM BY MEANS OF SUPERHEATED HEATING STEAM FiledFeb. 7, 1929 4 Sheets-Sheet 2 Fig. 3.

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QM WQ 4 Sheets-Sheet 5 H. TREDE ET AL Filed Feb. 7, 1929 July 4, 1933.

INDIRECT GENERATION OF STEAM BY MEANS OF SUPERHEATEID HEATING STEAM y1933- H. TREDE ET AL 1,917,166

INDIRECT GENERATION OF STEAM BY MEANS OF SUPERHEATED HEATING STEAM FiledFeb. 7, 1929 4 tsheet 4 Fig.5.

' Ivor/6211276: Jfana Trade and Ofla J1: Harfinann Patented Jul 4: 1933J y p sass rarest crates I HANS TBEDE AND OTTO H. HARTMANN,

ASS GENRES T0 SOHMEDTSCHE HEISSDAMPE-GESELLSCHAFT lVIIT BESCHRANKTER TU181G 01 KAESEL VJILH.ULMSHOHE, GERMALTY, A CORPORATIQN OF GER-MANY OIKASSEL-WILHELMSHOHE, GERMANY,

INDIRECT annnsii rion or srnaia BY MEANS or sUPnnHnA'rnn HEATING'STEAMApplication filed February '3", 1829, serial No.

heating element, the heat required for evap crating the Water in theboiler drum should be given up in the form of superheat and lat-v entheat; and in certain cases, moreover, part of the necessary heat istaken from the sensi ble heat of the condensed heatcarrier.

By reason of such requirements,definitelimits are imposed on the rangeof utility of known methods. 1

As a rule, the pressure of the heating steam: must be higher than thatof the steam generated, because only in such conditions is it p0;- ibleto impart the necessary heat content to the heating steam.

Our present invention affords a method by which steam can begenerateduindirectly by the use of the superheated steam Without thenecessity of satisfying the condition or requirement above set forth. f

On the contrary, it is possible to apply as the heat carrier heatingsteam of any desired pressure, and in particular steam of almv-pressure, and at the same time to generate Working steam of anyrequired pressure even up to the critical point.

V fith this object, successive transfers of heat to'the Water to beevaporated are eii'ccted by leadin superheated heating steam alternatelythrough superheater elements heated from the outside and through heatingelements lying in the evaporator drumn The present invention consists inthe use as heat carrier of Working steam which isled through heating onits Way from-the generator to thoengine, heat exchanger or the 7 e,Where it is used, the pressure oi genbeing higherth an the working" surethe place-Where it is used by such an amount that the difference ofpressure secures the i'lOW of heating steam through the stages. I

l Vith the new method ofivo'rkii no special auxiliary a;paratug such ascirculating pumps, necessary in or er to drive the heating steam throughthe heating elements, nor

338,156, and in Germany February 15, 1928.

is such a considerable degree of cooling required that the difference ofWeight of the heating steam in the inlet pipe and the condensate in theoutlet pipe is relied on to en sure floyvthrough the heating elements.

The number of heating stages is determined according to the conditionsof the particular case concerned.

For example, if high-pressure steam of 50 atmospheres is to be generatedand steam of 17 atmospheres superheated to 47 5 C, is used as heatingsteam and is taken in the form of saturated steam from an existingboiler plant, the number of heating stages is determined as follows:

The heat content of the heating steam of 17 atmospheres pressure andwith a superheat of 475 C. amounts according tothe usual steam table(Mollier entropy diagram) to 815kcal/ (g. In respect of this heatcontent, a fall oftemperature is available to the temperature of thesaturated steam to be generated at 50 atmospheres,that is to atemperature of about 268 0., the assumption that is 4.15 stages or inpractice 5, or to give a certain reserve, 6 heating stages would beprovided. o

If it is desired, With the same heating steam, to generate high-pressuresteam of 224 atmospheres, that is, of the critical pressure, heat mustbe supplied to the amount of 508200=808 kcal/kg. The temperature ofsaturated steam at 2% atmospheres is-about 374 0., and the heat contentof the heating steam of 17 atmospheres at this temperature is about 768kcal/kg. so that the available f heated to 4:75 6., and the temperatureof the heat is815763=52 kcal/k The number of heating stages is therefor?that is 5.92 stages.

In this way, for any desired pressure up to the critical pressure of theworking steam totity, then X-times the number of heating stages shown bythe above calculations must be used.

,lVith the present invention, the pressure of the heating steam can bechosen within wide limits and in particular steam of very low pressurecan be etliciently used as heating steam.

For example, it working steam of atmospheres is to be generated by meansof heating steam of 1.45 atmospheres superfeed water is C., then for theevaporation of a kilogram oi water at 105 C. in the Working boiler,664.5105, i. e., 559.5 kcals are necessary. From the steam table theheat content of the heating steam superheated to 475C is 818 kcal/kg.and at the temperature of the saturated steam to be generated at 50atmospheres, that is 263 C., it is 715 heal/kg, so that the heatavailable is 8lS-7l5=103 heal/kg.

- It will be seen, therefore, that in this case the number of stagesamounts to The necessary heatingsteam can be taken from any suitablesteam generator, for eX- ample, as mentioned above, from an existinglow-pressure boiler.

The present invention, however, is not confined to the application ofheating steam whose puressure is lower than that of the steam to begenerated. It is, for example, possible to utilize indirectly-generatedhighpressure steam as heating steam and to lead it from the evaporatordirectly without loss of pressure to the first heating stage. Further,if desired, the pressure of the heating steam taken from theindirectly-heated evaporator may be reduced before admission to theheating stages.

When heating up a boiler according to the present invention, it isimportant to provide for the generation of heating steam in theheating-stean'rsuperheater itself from dis tilled water introduced intothe first superheater stage, such water evaporating in the firstsuperheater stages and being superheated in the following stages.

In order, therefore, to accelerate the gen 5.43 stages.

eration of steam in the superheater, the pressure in the heating systemis reduced by leading the heating steam from the last heating stage intothe atmosphere or into a condenser.

For the generation of high-pressure steam of a given temperature inaccordance with the present invention, the choice of heating.

heatin sta es of the hi 'hressure'steam generator can be built into theexisting boiler.

The admission steam pressure of the existing engine installation isreduced in comparison with the pressure before alteration of the plant,so that in this way the pressure drop necessary for causing the heatingsteam to flow through the heating stages is obtained and the outletsteam coming from the heating stages may be admitted to a lowpressurestage of the engine In all cases, due to the fact that the flow ofheating steam through the heating stages is ensured solely by a pressuredrop between the heating-steam inlet and outlet, the advantage gainedthat the high-pressure evaporator may be arranged in any desiredposition, as, for example, at a level below that of the heating-steamgenerator.

In the accompanying drawings, different constructional forms of theinvention b vay of example are shown diagrammatically for carrying outthe present method of work Figure 1 shows a vertical section of anindirectly-heated steam generator applied to a marine cylindrical boilerof usual construction;

Figure 2 being a cross section on the line HII of Figure 1;

Figure 3 shows a longitudinal section of a modified form of a marinesteam boiler installation;

Figure shows a cross section of a station ary boiler plant; while iFigure 5 shows a longitudinal section of a locomotive and Figure 6 adiagram of a modified form of construction of a two-pressure boilerinstalla, tion.

In the form of the invention shown in Figures 1 and 2, the cylindricalboiler, 1, serves for the generation of the low-pressure steam whilehigh-pressure steam is generated in the drum, 2, by the indirect methodof heat ing. V

The hot gases from thefurnaces, 3, pass through the reversing chamber,4, and the cal boiler and the first super-heater element is connected aheating-steam pipe, 10, while from the heating element, 9,0f the lastheating stage, an outlet steam pipe, 11, is led to the outside of thesteam drum. The connecting pipes, 12, between a superheater element, 8,and the corresponding heating element, 9, as well as the connectingp1pes,1'3,

between a heating element,f9, and the next following superheaterelement, 8, are'each led respectively through one of the smoke tuhes,5,p I v The heatin'g'steam from the boiler, 1, flows therefore through theinlet" pipe, 10, into the. first superheater element, 8, then to thefirst heating element, 9, in the boiler drum and thence alternatelythrough a'superlnmter elementand an evaporator element till it passesfrom the last evaporator element, 9, through the exhaust pipe, 11,-tothe place where it is used. i

To the steam inlet pipe, 10, a feedpipe, let, is connected through whichin case of need distilled water can be introduced into the firstsuperheater stage, 8, so that in this Way heating steam can be generatedin the first heating stage itself. The necessity may arise,

for exam 31s in heatin u the boilerbefore the low-pressure boiler hasstarted'to make steam. In order to accelerate the generation o't'steamin the heating stages, the heating system is connected a pipe, 15,branching on from the outlet pipe, 11, toa condenser. By

a feed pi can be passed to the steam-and-wat'er drum, 2. Thehigh-pressure steamgenerated in the evaporator drum is led through apipe, 20, into a superheater arranged in the reversing chamber of thecylindrical boiler, 1, from which the superheated high-pressure steamflows through a pipe, 22, to the cylinder, and thence to the cylinder,24, of a-compound high-pressure engine. The steam'from the low-pressurecylinder, 24, exhausts into the heating-steam outlet pipe, 11, comingfrom the-heating sta es so that the hlgh-pressure exhaust steam is mixedwith the heating steam. As the temperature of the higb-pressure steamgenerated indirectly in the drum, 2, is substantial- 1y higher than thesaturated-steam temperature of the heating steam, the heating steamwhich each consists pe, 18,-provid'ed with a pump, 19, feed water fromthe low-pressure boiler, l,

flowing in the pipe, 11, from the heating stages is still superheatedand in consequence the mixture formed from the high-pressure exhauststeam and the heating steam is suit-' able for dolng work 1n alow-pressure steam ture does work in the cylinders, 26 and 27, of themachine installation originally present,

the new high-pressure cylinders, 23, 24, being added to the existingcylinders, 26, 27. The admission pressure of the steam to the cylinders,26-and 27, is reduced as compared with the corresponding pressure beforerebuilding so that compared to the admission pressure of the heatingsteam to the first heating stage, which corresponds approximatelyto theorig" inal boiler pressure, a sufficient pressure drop is provided toensure an eiiicient velocity of flow through the heating stages.

In the form of the invention shown in Figure 3, the heating steam isalso generated in a cylindrical boiler, 28, with smoke tubes, 29, theflow of hot gases corresponding to that of a ships boiler with returnflue. The furnace is not, however, arranged in the flue but in acombustion chamber lying below the boiler, 28,'this combustion chamber,30, being shut oif with respect to the boiler, 28, by acover, 31. i

The products of combustion from the furnace aredrawn rearwards into avertical fine, 32, which is formed by a cross wall, 34, introduced intothe reversing chamber, 33, the gases after passing through the fine, 32,

flowing through the reversing chamber, 33,

into the smoke tubes, 29, and thence to the uptake, 35.

The indirectly-heated steam-and-water drum, 2, liesabove the front partof the combustion chamber and is protected from the direct action of theheat o'fth'e furnace by 2 cover, 36.

Each ofithe successive heating stages, of

which for the sake of cleai*ness only four are'shown, consists as beforeof a superheater element-and a heating element. The supered. theheating-steam inlet pipe, 40, through which is led the heating steamgenerated in the boiler, 28. To the heating-steam inlet pipe, 40, isconnected a feed pipe, 41, through.

which'on heating up the installation distilled water may be fed into theheating element of the' first heating stage so that heating steam may begenerated in the superheater. The heatingsteam flows alternately throughasuperheater element, 38, and a heating ele-- incnt, 39, and is finallyled from the last heating element through the heating-steam outlet pipe,42, to the place where it is used. From the outlet pipe, 42, branchesoff a pipe, l3, by means of which the heating stages during heating upcan be connected to a co ndenser.. The highepressure steam generatedindirectly in the drum, 2, flows through a pipe, 44, to; a superheater,45, arranged in the flue, 32, and thence through a pipe, 46, to whereverit is required.

While in the form of the invention described, the heating steam isgenerated in a low-pressure boiler, in the stationary boiler shown inFigure 4, the heating steam is taken from the 'indirectlyeheatedhigh-pressure drum, 2, in a manner already known in :onnection withother methods of steam generation. T ie drum, 2, lies above the furnacewhich is provided with nozzles so that it may be tired either with oilor pulverized coal. The combustion chamber, 48, forms a vertical fluewhich at its upper end connected by a horizontal flue, 49, with asecondvertical line, 50, into which the hot gases are drawn in the directionfrom above downwards to the chimney. The h ating ele- \nents,'51, lyingin the steam drum, 2, as before, alternate with superheater elementsheated from the outside.

Three of the superheater elements shown, namely, the superheaterelements, 52, are arranged on the walls of the combustion chamber andreceive radiant heat from the furnace. In the fourth superheater elementare interposed the tubes, 53, forming in known manner acooling grate forthe slag while the superheater element, 54, to the last heating stage isarranged in the horizontal flue,.49. From the last heating element, 51,the heating steam is led first through a superheater, 55, lying in theflue, 50, and thence through a pipe, 56, to the place where it is used.I

In order to be able to generate heating steam in the superheaterelements of the heating stages during heating up, a steam pipe, 59,isconnected to the heating-steam inlet pipe, 58, leading to the firstsuperheater element, 52, while a pip-e, 60, leading to a condenser isconnected to the heating-steam outlet pipe, 56.

The high-pressure steam generated in the drum, 2, flows through a pipe,61, to a superheater, 62, lying in the flue, 50, and thence through apipe, 63, to the place where it is used.

Below the superheater, 62, in the fine, 50, a feed-water heater, 64, isarranged from which the preheated feed-water is led through a pipe, 65,to the steam drum, 2.

The superheater elements of the heating stages in this form of inventionare, as will be seen from the aboveexplanation, built and arranged in adifferent manner and are disposed essentially so that the superheatingelements through which the heating steam of higher pressure passes liewhere the highest combustion-chamber temperatures rule,

- while the following superheater elements corresponding to the fall inpressure of the heating steam as it passes through the heating stagesare arranged at points of lower temperature. This arrangement gives theadvantage that the heating steam. which has the greatest density flowsthrough the superheater elements subje'cted'to the highest temperatureso that the latter are efficiently cooled and protected from burnin Itis obvious that the area of the heating surfaces of the successiveheating stages must be designed to suit the above-mentioned conditions.

In the diagrammatic drawings this point, which is valid for all forms ofthe invention shown, has not been taken into consideration. In thelocomotive shown in Figure the heating steam is again generated in alowpressure boiler, in the present case of the longitudinal type, belowwhich'the steam drum, 2 is arranged.

The superheater elements, 69, of the heating stages which alternate withthe heating elements, 70, lying in the drum, 2, extend to the fire-boxthrough a large-diameter tube, 71, provided in place of the usual smoketubes. The heating steam is led from the steam drum, 73, through a pipe,74, to the heating element, 69, of the first heating stage and from theheating element of the last heating stage through a pipe, 75, tothelowpressure cylinder, 76, of the locomotive.

To the heating-steam inlet pipe, 74, as before, a feed-pipe, 78, isconnected and to the heating-steam outlet pipe, 75, a branch pipe,

79, through which the heating steam during heating up can pass into theatmosphere.

The high-pressure steam generated in the drum, 2, is led through a pipe80, to a superheater, 81, lying in the tube, 71 and the fireboX, 72, andthence through a pipe, 82, to the high-pressure cylinder, 8 V I Theexhaust steam from the high-pressure cylinder flows through a pipe, 84,to the heating-steam outlet pipe, 75, to mix therein with the heatingsteam before admission to the low-pressure cylinder, 76.

In contrast to the form of the invention shown'in' Figure 4, in whichfrom the inclirectly-heated steam drum only a part of the higl1pressuresteam is taken to serve as heating steam for the heating stages, whilethe other or larger part of the heating steam is led after superheatingdirectly to the engine, in the form of the invention shown in Figure 6,the whole of the high-pressure steam generated indirectly in the boilerdrum, 2, flowsthrough the heating stages before passing thence to theenglne.

The heat ng stages each consists of a superheater element, 85, arrangedas radiant heatreceiving surfaces in the furnace and heated from outsideand a heating element, 86, lying in the boiler drum, 2. To the firstsuperheater element, 85, is led the whole of the high-pressure steamfrom the drum, 2, through a pipe, 88. .This steam then flows alternatelythrough a superheater element,

85, anda heating element, 86, and passes from the last heating element,86, to the heatingstage outlet steam pipe, 89.

To the first superheater stage, 85, is connected a "feed pipe, 90, andto the outlet pipe, 89, is connected a branch pipe, 91, through which,when heating up, the outlet-steam pipe can be connected to atmosphereorto a condenser. he exhaust steam pipe, 89, is connected by w y of acontrol valve, 92, with a sup-erhcater, 95, lying in the smoke tubes,93, of a smoke-tuhe boiler, 94, from which su'erheater a pipe, 96, leadsto the high-press 1 stage ofthe engine In addition, a branch pipe, 99,provided with a control valve, 98, is led from the outletsteam pipe, 89,into the water space of the smoke-tube boiler, 94. It the valve, 98, isclosed, all the high-pressure heating steam passes through wsuperheater, 95, and the pipe, 96,,to toe high-pressure stage of theengine after it has served in the heating stages by alternatesuperheating and giving up heat to generate high-pressure steamindirectly in the drum, 2. i

The admission pressure in this stage of the engine isso much less thanthe working pressure in the drum, 2, that the necessary veloci y of flowis ensured through the heating taees.

Since, in the heating elements, 86, and especially in the last heatingstages, the heating-steam pressure is less than the working in theheating elements cannot cool down to pessure in the drum, 2, the heatingsteam a temperature cmrespondinpto the tempera ture of saturated steamat this lower heating steam pressure, andconsequently cannot condensewhen flowing through the heating ele-' ments.

On the other hand, the result of opening the valve, 98, is that a partoi the heating steam coming from the heating stages flows into the waterspace of the low-pressure boiler, 94:. This traction of" the heatingsteam flowing into the low-pressure boiler, 94, can be regulated byappropriate adjustment of the two valves, 92 and 98.

In the case when all the heating steam is admitted into the low-pressureboiler, the necessary pressure drop is likewise obtained in order tosecure an el'licient flow of the heating steam through the heatingstages.

The steam generated in the low-pressure hoiler,,91, flows through apipe, 100, to a superheater, 101, arranged in the smoke-tubes,

93, of the boiler, 94, and thence through a pipe, 102, to thelow-pressure stage of the engine.

What we claim is:

1. Steam generating plant comprising in combination an indirectly heatedsteam boiler, a source of heating steam, and heating said water and thenalternately superheating' it and passing it in heat exchangerelationship with said water without mixing it therewith a plurality oftimes, and finally utilizing it at a pressure lower than its initialpressure thereby to induce a flow thereof.

3. Steam generating plant comprising a boiler drum, a plurality ofheating elements in the drum, a plurality of superheaters, said heatingelements andsuperheaters being alternately connected. in series, and aconduit connecting the steam space of said drum with said seriesconnected superheaters and heating elements.

4. In a multi-stage boiler installation generating working steam at aplurality of pres sures in a plurality of sections for discharge to aplurality of working points, a plurality of heating elements in one ofthe sections, a

plurality ot superheaters in the path of the furnace gases, said heatingelements and suerheaters beine alternately connected in series, and aconduit connecting the steam space of one of the boiler sections withsaid series connected superheaters and heating elements to supply steamto said elements at a pressure not greater than that of the steam in thesection containing the heating elements. 5. The method of continuouslygenerating steam from a body of water, which. comprises successivelypassing heating steam in heat exchange relation with a flow of hot gasesto'superheat the same and then passing the thus superheated heatingsteam in heat exchange relation with said water a plurality of times,and finally utilizing theheating steam for the performance of mechanicalwork at a pressure lower than its initial pressure, the heating steambeing at least a portion of the steam generated from said body of water.

' In testimony whereof we affix our signatures.

HANS TREDE. OTTO H. HARTMANN.

